The present invention relates to organic electroluminescent devices, methods for producing the organic electroluminescent devices, and electronic appliances.
In recent years, development of light-emitting devices using organic materials has been accelerated to provide self-emitting displays as an alternative to liquid crystal displays. Vacuum deposition and wet deposition, for example ink jetting (droplet ejection), are used in known methods for producing such organic electroluminescent devices (referred to as organic EL devices throughout the present specification) using an organic luminescent material. According to a method using vacuum deposition (for example, see Patent Document 1), a luminescent material with a low molecular weight is vaporized while a substrate and the evaporation source are opposed with a mask disposed therebetween, thereby forming a luminescent layer corresponding to the pattern of the mask. According to a method using ink jetting, on the other hand, a liquid material containing a polymeric luminescent material is ejected (applied) according to pattern data, such as a bitmap, to form a luminescent layer corresponding to the pattern data.
Ink jetting allows the ejection and application of droplets with a diameter on the order of micrometers at high resolution, thus offering high-resolution patterning. This method, in which a liquid material is ejected only to a predetermined pattern, also has the advantage that it produces no waste of material and therefore allows the production of organic EL devices at low cost.
In addition, methods for forming relatively lyophobic and lyophilic parts on a substrate are generally known as a preliminary process for ink jetting. For example, a method is known in which a lyophobic resin insulating layer and a lyophilic silicon oxide layer are deposited. Also, a method for forming a lyophilic pattern has recently been known in which a self-assembled lyophobic film is formed on the overall surface of a substrate and is irradiated with ultraviolet light through a mask to partially remove the lyophobic film (for example, see Patent Document 2). In either method, a liquid material landed on the lyophobic part can be allowed to flow toward and remain at the lyophilic part.
An organic EL device produced by ink jetting after the deposition of the lyophobic and lyophilic parts is described below.
FIG. 11(a) is a partial sectional view of the organic EL device. In FIG. 11(a), reference numeral 300 indicates a pixel electrode, reference numeral 301 indicates a silicon oxide layer (lyophilic part), reference numeral 302 indicates a resin insulating layer (lyophobic part), reference numeral 303 indicates a hole-injection layer, reference numeral 304 indicates a luminescent layer, and reference numeral 305 indicates a cathode. The hole-injection layer 303 and the luminescent layer 304 are in contact with the resin insulating layer 302 because they are formed by applying liquid materials using ink jetting. When the solvent contained in the liquid materials is dried, the hole-injection layer 303 and the luminescent layer 304 have a thickness profile (cross-sectional shape) that is thinner at its central part xc and is thicker at its ends x1 and x2.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 9-204985.
[Patent Document 2] Japanese Unexamined Patent Application Publication No. 2002-237383.